CN102237826A

CN102237826A - Power tracing method of photovoltaic system, photovoltaic system and power conversion system

Info

Publication number: CN102237826A
Application number: CN2011101562638A
Authority: CN
Inventors: V·布哈瓦拉珠; R·P·佩普林斯基; A·普拉萨
Original assignee: Eaton Corp
Current assignee: Eaton Corp
Priority date: 2010-03-23
Filing date: 2011-03-23
Publication date: 2011-11-09
Also published as: US20110232714A1; US9502904B2; CA2734671A1; MX2011003108A

Abstract

A power conversion system includes a number of photovoltaic arrays, a number of inverters, a transformer, and processor. The processor is structured to control the number of inverters and operate the power conversion system to provide maximum efficiency of power conversion by the number of photovoltaic arrays, the number of inverters and the transformer, and to maximize power output from the number of photovoltaic arrays.

Description

The power method for tracing, photovoltaic system and the electric power coversion system that are used for photovoltaic system

Technical field

Disclosed design relates generally to particularly be used for the electric power coversion system of PV system to changing from the energy of photovoltaic (PV) array.The invention further relates to the energy transformation method that is used for the PV system.The present invention also relates to the PV system.

Background technology

Photovoltaic (PV) array typically is configured with the series connection of a plurality of photovoltaic modules/be arranged in parallel.Traditional way is to guarantee under the condition of worst case, and direct current (DC) voltage that the photovoltaic module string produces is no more than the insulation rating of PV module.For example, National Electric Code (NEC) requires this voltage to be lower than 600VDC.

Exemplary PV array/inverter system 2 as shown in Figure 1.A plurality of strings 8 of two exemplary light photovoltaic array 4,6 each freedom photovoltaic module 10 that is electrically connected in parallel before the PV of correspondence array is electrically connected to inverter 12 are formed.

For example, the PV module depends on the temperature of PV module, the condition on PV module surface, aging (age) and the technology of PV module of PV module for the electric power output of a solar radiation grade.Yet the direct current (amperage) 16 of the direct voltage of PV array (voltage) 14, PV array and the direct current power of PV array output (wattage) 18 about the general characteristic of 100% solar radiation (i.e. " sunshine ") 20 as shown in Figure 2.Also show the curve 22 of array output current vs. array output voltage.

Once again referring to accompanying drawing 1, for example, before for example injecting city's electrical network 24, converted to interchange (AC) electric power by electric power converter (for example, inverter 12) from the direct current power of PV array 4,6.Be preferably, electric power converter 12 is guaranteed the direct current power maximization from PV array 4,6.Energy maximization from PV array 4,6 is constantly to change working point (operating point) by the temperature based on solar radiation and PV module 10 to carry out.Yet, have multiple conversion efficiency from the direct current power to the alternating electromotive force.For example, power conversions can be finished by the electric power converter (not shown) more than.When using more than one electric power converter, efficient depends on the working point of a plurality of electric power converters.In addition, the secondary array that is connected to each electric power converter can have the different secondary array operating voltage for maximum power.

In this power conversions process, there is extra poor efficiency in the transformer 26 between inverter 12 and city's electrical network 24.As shown in Figure 3, the

exemplary efficiency curve

28,30 of inverter 12 and transformer 26 has the convex characteristic.The efficient of inverter depends primarily on DC input voitage, inverter switching frequency and operating current.The efficient of transformer 26 depends on design and working point.

There is improved space in the electric power coversion system that is used for the PV system.

Also there is improved space in the power transferring method that is used for the PV system.

There is further space in the improvement of PV system.

Summary of the invention

Because the cost of solar energy module and installation thereof is higher relatively, in order to obtain the economic feasibility of solar energy PV power conversions, it is very important extracting ceiling capacity from photovoltaic (PV) array, inverter and transformer.

Among one day,, make PV array, inverter and transformer extremely important with its corresponding maximal efficiency work along with sunlight conditions and PV module variation of temperature.When inverter is not that the efficient of transformer is fixed for design when being in its peak efficiencies, and the efficiency characteristic of transformer is selected as having near the peak efficiency 100%.

Two or can be operated to more than two inverter and to make PV array output maximization individually.Based on output AC electric power, can advantageously select the quantity of inverter and the quantity of PV array independently.

But when the energy storage time spent, except energy conversion efficiency, this system can carry out optimization from economic angle.

These and other demand is realized by the embodiment of disclosed design, except that the output maximization that makes from the PV array, embodiment is also by (for example moving the PV system with maximum conversion efficiency, be not limited to, the PV array, corresponding energy converter and single transformer) energy that injects city's electrical network and/or load is maximized.

According to the one side of disclosed design, a kind of power is followed the trail of (power tracking) method and is used to comprise the photovoltaic system of several photovoltaic arrays, several inverters and transformer.This method comprises: operation comprises the photovoltaic system of described several photovoltaic arrays, described several inverters and transformer, so that provide maximum power conversion efficiency by it; Make power output maximization from described several photovoltaic arrays.

This method may further include, with a plurality of photovoltaic arrays as described several photovoltaic arrays, and with the output-parallel of described a plurality of photovoltaic arrays.

This method may further include, and a plurality of photovoltaic arrays are used as described several photovoltaic arrays; A plurality of inverters are used as described several inverters; For in described a plurality of photovoltaic arrays each, power supply of a correspondence in described a plurality of inverters of the correspondence from described a plurality of photovoltaic arrays; Produce or be approximately in the process that peak energy produces at peak energy, make in described a plurality of photovoltaic array each be operated in corresponding independent maximum power point.

This method may further include, and determines the energy and the power of city's electrical network, determines the loading (loading) on described several inverters and the transformer, and makes system works at optimum pressure level (stress levels).

This method may further include, two photovoltaic arrays are used as described a plurality of photovoltaic arrays, two inverters are used as described a plurality of inverters, when initial, with the output-parallel of two photovoltaic arrays and by the power supply of parallel connection output in two inverters, determine when surpass predetermined power percentage from described one the power output in two inverters, in response by one in two photovoltaic arrays described power supply in two inverters, and by another another power supply in two inverters in two photovoltaic arrays, make described described one maximum power point that is operated in two photovoltaic arrays in two inverters, make described another in two inverters be operated in described another maximum power point in two photovoltaic arrays.

This method may further include, and determines from two inverters when the two power output drops to be lower than predetermined power percentage; At the fixed time in the interval, determine when described one in two inverters moved and be longer than the scheduled time, forbid in two inverters described one in response, the output-parallel of two photovoltaic arrays and should parallel connection output another power supply in two inverters.

As disclosed design on the other hand, a kind of photovoltaic system comprises: energy storing device; Photovoltaic array; Transducer, it comprises and being constructed to from energy storing device input electric power or to first I/O of energy storing device output power and second I/O that is constructed to import electric power or output power; Inverter, it comprises and being constructed to from the input of photovoltaic array input electric power and the output that is constructed to output power; Transformer, its have the output that is connected electrically to inverter and transducer second I/O former side (primary) and be connected electrically to local load and city's electrical network at least one pair side (secondary).

First I/O of transducer can be imported electric power from energy storing device, the exportable electric power of second I/O of transducer, and local load can be passed through transformer-supplied by transducer and inverter.

Transducer can be constructed to as the voltage source operation, and uses frequency and the voltage that local load is set from the available power of energy storing device.

First I/O of transducer can output to energy storing device with electric power, and second I/O of transducer can be imported electric power, and local load can be passed through transformer-supplied by inverter.

Transducer can be to be configured to active rectifier that energy storing device is charged.

Second I/O of active rectifier can be crossed transformer-supplied by civil power Netcom.

Described first I/O of transducer can output to energy storing device with electric power, and second I/O of transducer can be from the output input electric power of inverter.

Local load or city's electrical network can not be powered, and second I/O of transducer can directly be imported electric power from the output of inverter.

The pair of transformer can be only to be connected electrically to local load, first I/O of transducer can be imported electric power by energy storing device, the exportable electric power of second I/O of transducer, local load can be passed through transformer-supplied by transducer and inverter.

Transducer can be constructed to as the voltage source operation, and the frequency and the voltage of local load are set, and inverter can be constructed to follow the trail of the frequency and the voltage of local load.

As disclosed design on the other hand, electric power coversion system comprises: several photovoltaic arrays; Several inverters; Transformer; Processor, this processor is constructed to, control described several inverters, the electrical power for operation converting system, providing the maximal efficiency of power conversions, and make power output maximization from described several photovoltaic arrays by described several photovoltaic arrays, described several inverters and transformer.

Described several photovoltaic arrays can be two photovoltaic arrays that have output separately, described several inverters can be two inverters, and processor can be constructed to selectively to make: (a) one of the correspondence in the inverter is by power supply of the correspondence in two photovoltaic arrays; Or (b) output-parallel of two photovoltaic arrays is electrically connected, and one in two inverters by parallel connection output power supply.

Description of drawings

To the introduction of preferred embodiment, will obtain complete understanding below reading in conjunction with the accompanying drawings to disclosed design, in the accompanying drawings:

Fig. 1 is the block diagram of photovoltaic (PV) array/inverter system;

Fig. 2 is the curve chart for the 100% solar radiation PV array voltage at (i.e. " sunshine "), electric current and power output;

Fig. 3 is the curve chart for the efficient vs. percentage load of transformer and inverter;

Fig. 4 is the block diagram according to the electric power coversion system of the embodiment of disclosed design;

Fig. 5 is the curve chart of solar radiation, the time in the middle of one day and inverter system capacity, and it shows the seasonal variety of solar energy capacity utilance of the electric power coversion system of Fig. 4;

Fig. 6 is the block diagram of schematic diagram form of electric power coversion system that comprises Fig. 4 of system control;

Fig. 7 is the curve chart of efficient vs. percentage load of electric power coversion system, transformer and the inverter of Fig. 4;

Fig. 8 is the flow chart by the program of the system controller execution of Fig. 4;

Fig. 9 is that the electric power coversion system of Fig. 4 is for the PV array output power of two different level of solar radiation and the curve chart of PV array output voltage;

Figure 10 is the curve chart that the fault of converter periodicity vs. radiator temperature of the electric power coversion system of Fig. 4 changes;

Figure 11 A-11E is the block diagram that comprises the energy storing device that demonstrates the difference operation that improves the output of PV array energy according to other embodiment of disclosed design;

Figure 12 is the flow chart of the program carried out of the system controller of Figure 11 A.

Embodiment

As used herein, one of term " several " expression or greater than one integer (that is, a plurality of).

As used herein, term " processor " expression can be stored, the programmable analog and/or the digital device of retrieval and deal with data; Computer; Work station; PC; Microprocessor; Microcontroller; Microcomputer; CPU; Master computer; Microcomputer; Server; Network processing unit; Controller; System controller; Programmable logic controller (PLC); Or any suitable processing unit or equipment.

As used herein, term " inverter " expression becomes electric energy the equipment or the device of form of communication from the direct current formal transformation.

As used herein, device or equipment that term " transducer " expression is such: its on first direction with electric energy from the direct current formal transformation become form of communication (such as but not limited to, as inverter) by the power supply of dc energy storage device, and/or on opposite second direction with electric energy from form of communication convert to the direct current form (such as but not limited to, as active rectifier or other rectifiers, so that the dc energy storage device is charged).

Referring to Fig. 4, the different energy conversion efficiency in the multi-inverter electric power coversion system 50 is shown in the

triangle

40,42,44,46,48.In each triangle, there is the working point of maximum power.Based on available power, electric power coversion system 50 can be reconfigured to obtain optimal conversion efficiency.The alternate configuration of this electric power coversion system 50 can be the independent transformer (not shown) that has for two

exemplary inverter

52,54, but 70 to two transformers of a transformer have higher efficient relatively.

Exemplary power converting system 50 comprises three kinds of different exemplary operational modes: each in (1) two

exemplary inverter

52,54 is operated in the maximum power point that is electrically connected

corresponding PV array

56,58 thereon respectively; (2) first inverters 52 are only worked under two

PV arrays

56,58 are connected electrically to the situation of this inverter; (3) second inverters 54 are only worked under two

PV arrays

52,54 are connected electrically to the situation of this inverter.

Exemplary power converting system 50 comprise two

inverters

52,54 and be connected respectively to two

PV arrays

56,58 of two inverters 52,54 (such as but not limited to, be of different sizes).When the output of combination PV array is lower than the capacity of an inverter, only inverter 52 or 54 work.So this inverter makes from the power output maximization of combination PV array 56,58.When the output of combination PV array during greater than the capacity of an

inverter

52 or 54,

PV array

56,58 is shared between two corresponding inverters 52,54.So two

inverters

52,54 make

corresponding PV array

56,58 be operated in its corresponding peak power output.Preferably, by adjust the PV array voltage in disconnection or before connecting the PV array, two

inverters

52,54 conversions (transition) smoothly between two

PV arrays

56,58 at every turn.Will be seen that although only show two exemplary inverter, this system or other electric power coversion systems can be worked under the situation more than two inverters.

In second mode of operation, processor---for example system controller 60 (such as but not limited to programmable logic controller (PLC) (PLC)) (Fig. 6)---is communicated by letter with two

inverters

52,54 and wattmeter 62 (Fig. 6) (such as but not limited to using suitable communication channel or network; Modbus; RS-485).For example, every day, first inverter 52 wakes (wake up) in the morning up, be connected electrically to city's electrical network 64 and under the situation of contactor K266 closure (i.e. the output of two

PV arrays

56,58 all is electrically connected) export electric power to the city electrical network.

Along with the variation of a time, electric power output increases, and the loss of first inverter 52, its filter 68 and transformer 70 increases.When the output of first inverter 52 reaches suitable predetermined power percentage (such as but not limited to about 80% as wattmeter 62 is measured; The percentage of any appropriate) time, the loss in first inverter 52 will be above the loss under the condition of all working at two inverters 52,54.System controller 60 uses this predetermined power percentage recently to connect second inverter 54 and disconnect contactor K266 (as shown in FIG.).This is first mode of operation, and wherein, 52,54 work of two inverters are also shared the PV array energy of its corresponding PV array 56,58.First inverter 52 is operated in the maximum power point of PV array 56, and second inverter 54 is operated in the maximum power point of PV array 58.Two

inverters

52,54 have altogether than inverter 52 that works independently or 54 relative higher energy and power efficiencies.When the cloudy day, only there is an

inverter

52 or 54 to work fully, work with two

inverters

52,54 thus or use a relatively large inverter (not shown) to compare and save considerable loss, therefore increase energy output from

PV array

56,58.

Below, make the maximized control of energy in conjunction with what Fig. 8 discussed that

inverter

52,54 uses from its corresponding PV array 56,58.When total percentage power drops to suitable predetermined power percentage (such as but not limited to about 80%; When the percentage of any appropriate) following, and for example first inverter 52 worked surpass one day the scheduled time (such as but not limited to 4 hours; The time of any appropriate) time, first inverter 52 cuts out and contactor K266 closure, makes second inverter 54 obtain whole outputs of two PV arrays 56,58.This 3rd mode of operation guarantees that the hours worked of two

inverters

52,54 is identical or roughly the same.

As will discussing in conjunction with Fig. 7 and Fig. 8, electric power coversion system 50 operation

example PV arrays

56 and 58,

exemplary inverter

52 and 54 and exemplary transformer 70 are so that provide the maximal efficiency of power conversion from it.For example, referring to Fig. 7 for peak value to second curve Figure 92 of system of the hope percentage power output of the city's electrical network 64 of Fig. 4 or local load (not shown).

Exemplary diurnal variation curve Figure 72,74 of the position solar radiation that Fig. 5 shows and using " trackings " (obscuring with the power points tracking) PV array---for example the

exemplary PV array

56,58 of Fig. 4---.For example, such Tracing PV array can use two axles or three axle (not shown), and these sun-tracings also keep PV module (not shown, but can referring to the PV module 10 of Fig. 1) and incident solar radiation perpendicular.Fixing PV array (for example, having fixing angle with respect to the sun) (not shown) is not followed the trail of sun's motion in a day, and has the curve with the slightly narrower of PV array 56,58.Also there is seasonal variations in exemplary summer between curve 72 and the exemplary winter curve 74.Certainly, in the fine period in one day,

inverter

52,54 is not operated in the full capacity state, therefore, exists and adopts the possibility of selecting best configuration as following suitable procedure in conjunction with Fig. 8 discussion.Such as but not limited to, for being provided, higher relatively energy exports the also utilization rate of

balance inverter

52,54, and at noon can be in the some hrs after Zhi Qian some hrs and high noon with the output-parallel of

PV array

56,58.

The electric power coversion system 76 that comprises suitable system's control architecture illustrates at Fig. 6.Two

exemplary inverter controllers

78,80 by system controller 60 controls are operated two

exemplary inverter

52,54 with electrical network paralleling model (grid parallel mode) (for example, being limited by IEEE 1547 and UL 1741).Enter the power output of corresponding transformer 70 (transformer only is shown among Fig. 6) by system controller 60 controls at the inverter 52 of correspondence or 54 output place.Be electrically connected at the wattmeter 62 at city's electrical network 64 places and measure the three phase power that enters city's electrical network aptly.System controller 60 is also controlled the parallel connection of the

DC bus

82,84 that enters two corresponding inverters 52,54.Based on output of the power of

inverter

52,54 and efficiency curve, whether two

inverters

52,54 work alone in system controller 60 decisions, perhaps, and whether only work in two inverters 52,54.When two

inverters

52,54 are sending ionization from two

discrete PV arrays

56,58, the output of two inverters of system controller 60 controls.Then, the dc voltage on the

PV array

56,58 of independent

circuit control device

78,80 adjustment correspondences.

When in case of necessity, the contactor K266 between two

DC buses

82,84 is closed or disconnect; In this process, the electric power transfer that system controller 60 is coordinated from an inverter 52 to another inverter 54.

Fig. 7 comprises the curve Figure 86,88,90 that exports (load) percentage for efficient (%) the vs. power of one in corresponding transformer among Fig. 4 70, two

inverters

52 and 54 and system 50.System effectiveness under the situation that the operate as normal of two

inverters

52,54 is moved is always illustrated by the curve Figure 90 of system.In two

inverters

52,54 one is illustrated by second curve Figure 92 of system for the improved system effectiveness under the situation of 50% power operation.Can be easy to see, if two

inverters

52,54 as will in conjunction with Fig. 8 discussion, working in selectable mode, efficient can be higher under multiple power output percentage.

Fig. 8 is that it comprises maximum power point tracking (MPPT) by the flow chart of the program 100 of system controller 60 execution of Fig. 4.

Circuit control device

78,80 among Fig. 6 is measured the dc voltage of

corresponding PV array

56,58 and is reported to system controller 60.At first, at 102 places, program 100 judge under the situation of contactor K266 closure the dc voltage of

DC bus

82,84 whether be higher than suitable wake-up voltage (such as but not limited to, 400VDC).If, judge that the voltage of city's electrical network 64 and frequency are whether in the scope of the limits value of hope so at 104 places.If the judged result at 102 or 104 arbitrary places enters resting state at 106 places so for not.Then, after the suitable time, repeating step 102.Otherwise, if the voltage of city's electrical network and frequency are in the scope of the limits value of hope, so, at 108 places, in the system controller 60

control inverter controllers

78,80 one is so that make a beginning switch in the corresponding

inverter

52,54 with driver transformer 70.

Next step, at 110 places, judge two

inverters

52,54 the two (such as but not limited to, as merging from

circuit control device

78,80 by system controller 60) system's power output whether greater than predetermined power value (such as but not limited to, No load pwr=600W).If, do not enter park mode at 106 places so.On the other hand, if inverter power greater than the predetermined power value, so at 112 places, judges whether PV voltage (dc voltage of

DC bus

82,84 under the situation of contactor K266 closure) is higher than predetermined value (such as but not limited to, Min Vdc=400VDC).If, do not enter park mode at 106 places so.Otherwise, if the PV direct voltage greater than this predetermined value, so at 114 places, system controller 60

control inverter controllers

78,80 are so that make corresponding

inverter

52,54 and city's electrical network 64 synchronously and then make contactor K167 closures.

After 114, at 116 places, in two circuit control devices 78,80 of system controller 60 control one is to start the direct current MPPT in the corresponding inverter 52,54.In this stage of program 100, only circuit control device 78 starts direct current MPPT.Next, at 118 places, judge that according to wattmeter 62 power that flows into city's electrical networks 64 is whether greater than a predetermined value (such as but not limited to, Min Pwr=200W).If, do not enter park mode at 106 places so.On the other hand, if the power that flows into city's electrical network 64 greater than this predetermined value, so at 120 places, according to wattmeter 62 judge flow into city's electrical networks 64 power whether greater than a predetermined value (such as but not limited to, 80%; 85% of Max Pwr=110kW or inverter 52,54 rated values; 80% of Max Pwr=100kW or inverter 52,54 rated values; The value of any appropriate).If yes, so at 122 places, contactor K266 disconnects, contactor K1-271 closure, and two circuit control devices 78,80 of system controller 60 controls start two direct current MPPT on the corresponding inverter 52,54.For better energy efficient is provided, during peak energy produced or is approximately the time period of peak energy generation, its independent maximum power point place in correspondence moved each PV array 56,58.

Next, at 124 places, according to wattmeter 62 judge enter city's electrical network 64 power whether less than predetermined value (such as but not limited to, 80%; Max Pwr; Exceed 200% 80% (80%out of 200%for one inverter 52,54) for an inverter 52,54; The value of any appropriate).If deny, so at 126 places, monitor the DC power output (for example, use wattmeter 62 or pass through in system controller 60, to merge output) of two inverters 52,54, after this, at 128 places, all startup exchanges MPPT on two inverters 52,54.System controller 60 adopts the efficiency curve of combination inverter and voltage transformer system to carry out pre-programmed, so that select to be used for the maximal efficiency point of work.In order to be operated in the working point of hope, inverter 52,54 is provided with the Power Limitation value that will satisfy based on combined system efficient.System controller 60 can to from the AC power of wattmeter 62 output carry out integration to determine the output energy, perhaps, wattmeter 62 can advantageously provide performance number and energy value the two.Then this information can be used to determine the loading (for example, power percentage) of inverter 52,54 and transformer 70 by system controller.

Next, at 130 places, judge that whether (for example, the output of inverter whether drop to be lower than the Power Limitation value) AC power is less than a predetermined value (for example, Max Pwr).If then repeating step 126 not.Otherwise, at 132 places, contactor K266 closure, in two inverters 52,54 one is depended on the running time of each inverter 52,54 and is stopped, to enter the 3rd mode of operation, this hours worked of having guaranteed two inverters 52,54 is identical or roughly the same.Such as but not limited to, step 132 can preset time at interval (such as but not limited to, one day; Judge the time of any appropriate) when in two inverters 52,54 one moves and be longer than a scheduled time (such as but not limited to, 4 hours; The time of any appropriate).This is with the electric power coversion system 76 among optimum pressure level run Fig. 6, thus the life-span of growth inverter 52,54.For example, by operation every day inverter 52 or 54 alternately, the variation of inverter radiator temperature (referring to accompanying drawing 10) is lowered.After 132, execution in step 116 is to start the direct current MPPT on that is moving in two inverters 52,54.

Fig. 9 (for example illustrates two different level of solar radiation, be respectively 100% radiation and 80% radiation) under curve Figure 140,142 of PV array output power vs.PV array output voltage, it comprises effective VD working range of the

inverter system

50,76 in Fig. 4 and 6.Utilize this information, system controller 60 can be determined the optimum PV array voltage under the given level of solar radiation, thereby makes

PV array

56,58 be operated in maximum power output place for specific solar radiation.Along with wearing out of

PV array

56,58, the power output that same electrical is depressed will reduce.This method is not to seek absolute power level, obtains maximum power but seek.

What another will be considered is the control of PV array 56,58 in a day.When the output of PV array when an A 144 is changed to a some B 146, inverter 52 or 54 voltages are set to Vpv B and store the voltage and current of corresponding PV array.After a suitable time delay, the variation that inverter 52 or 54 is sought electric currents judges that also electric current is to increase or reduce.Next, use the positive sequence voltage in city's electrical network 64 to judge that line voltage is increase or reduces.The symbol that changes based on electric current and the symbol of grid voltage change, contravarianter voltage set-point 148 (as shown in phantom in Figure 9) are about Fig. 9 to the right or be moved to the left.The tracking from the available horsepower of PV array 56 or 58 is guaranteed in this control, and for inverter 52 or 54 and PV array 56 or 58 stable operating voltage is provided.After each interval, preserve power output from two inverters 52,54 of combination.This output power information is used to judge several will the operation in two exemplary inverter 52,54.When two array voltages that are connected to two inverters 52,54 were controlled in its corresponding Vmp (voltage during maximum power), because the variation of PV array 56,58, efficient can be higher.When PV array 56,58 was controlled (this point realizes by the contactor K266 in the fragmentary 6) discretely, system controller 60 can have the power level of learning ability or user's selection.This be because can exist PV array and PV array difference (such as but not limited to, up to about 3%, it can be called the factor of not matching) and the difference of transformer and transformer.

This can combine on their maximum power point (referring to the triangle among Fig. 4 40,42,44,46,48) with other operate system components---as transformer and inverter---.The disconnection of contactor K266 can be determined by the learning algorithm in the system controller 60 as previously described.

Figure 10 shows curve Figure 150,152,154 of typical life (for example, inaction interval number) the vs. variations in temperature of inverter.The inverter that (rotate) starts in the morning because the disclosed method of two

inverters

52,54 of use circulates in turn (such as but not limited to, inverter 52), the variations in temperature of two

inverters

52,54 has reduced half.Second inverter that started after a while on the same day (such as but not limited to, inverter 54) identical variations in temperature can not appear, because the shell (not shown) was heated in the time period in the morning.

With reference to Figure 11 A-11E, two other exemplary power converting system 160 (Figure 11 A-11D) and 162 (Figure 11 E) comprise the energy storing device that is connected electrically to first transducer 166---for example exemplary storage battery 164---and be connected electrically to the PV array 176 of second inverter 170.

Figure 12 shows the program 172 that the system controller 174 among Figure 11 A is carried out.By using energy storing device 164 with transducer 166 and using PV array 176 with inverter 170, the PV energy management is different from the PV energy management of the electric power coversion system 50 among Fig. 4.Operated inverter 170 is so that from the maximizes power of PV array 176, transducer 166 is for energy storing device 164 management energies.What can be sure of is, the system that uses energy storing device, PV array and multi-inverter and/or transducer is novel in non-obvious.

With reference to Figure 11 A, comprise that the exemplary inverter/transducer electric power coversion system 160 of PV array 176 and energy storing device 164 is connected electrically to local load 178 and exemplary city's electrical network 180.In this electric power coversion system 160, transducer 166 is connected electrically to energy storing device 164 (such as but not limited to, battery; Electric double layer capacitor; Farad capacitor device (super-capacitor); Electrochemical double layer capacitor (EDLC); Ultracapacitor (ultra-capacitor)), inverter 170 is connected electrically to PV array 176.Under this pattern, inverter 170 provides the maximum power point tracking of corresponding PV array 176 by the output voltage of adjusting the PV array continuously, so that from wherein receiving maximum power.Controller 182 and 184, wattmeter 186,

filter

188 and 190 and transformer 192 with Fig. 6 in corresponding

controller

78 and 80, wattmeter 62,

filter

68 and 69 and transformer 70 similar modes move.

Transducer 166 has and is constructed to from energy storing device 164 input electric power or to first I/O 165 of its output power and second I/O 167 that is constructed to input or output electric power.Inverter 170 has the input 169 and the output 171 that is constructed to output power that is constructed to from PV array 176 input electric power.Transformer 192 comprises former side 191 and pair side 193, former side 191 is connected electrically to inverter output 171 and is connected electrically to second I/O 167 of transducer by filter 188 by filter 190, and pair side 193 is connected electrically at least one in local load 178 and the city's electrical network 180.

In Figure 11 B, when being connected to city's electrical network 180, local load 178 is by PV array 176/

inverter

170 and 166 both power supplies of energy storing device 164/ transducer.Therefore, when the power output of PV array was not enough to satisfy the demand of local load 178 and therefore the power output of inverter 170 is not enough to satisfy the demand of local load 178, transducer 166 was by discharging the energy that is stored in the energy storing device 164 and replenishing electric power to local load 178 to local load 178.Under this pattern, depend on available power from inverter 170, transducer 166 is constantly managed local load 178.

Shown in Figure 11 C, when inverter 170 can be when local load 178/ city's electrical network 180 transmits whole electric power, as required, for example enter the active rectifier pattern and energy storing device 164 is charged thereby transducer 166 changes its controls.If the power output of inverter 170 exceeds loading demand, transducer 166 also can charge to energy storing device 164.

In Figure 11 D, there is not energy to be sent to local load 178/ city's electrical network 180, be used for charging from whole energy of PV array 176/ inverter 170 by 166 pairs of energy storing devices 164 of transducer.Under this pattern, energy is not transferred to energy storing device 164 by output transformer 192 from PV array 176.What can be sure of is that this is electric power coversion system 160 novelties and non-obvious feature.Since electric power does not transmit by transformer 192 and in the most of the time igbt (IGBT) (not shown) of transducer 166 do not need switch, this method has also improved the efficient of electric power coversion system 160.For example, the ac output voltage amplitude that is connected to the inverter 170 of PV array 176 is higher than the direct voltage of energy storing device 164.Transducer 166 does not need the seedbed AC is carried out rectification.For example, the inverse parallel diode (not shown) that is connected across between the IGBT (not shown) two ends of transducer 166 can be used to rectification.

Shown in Figure 11 E, another inverter/transducer electric power coversion system 162 is powered to local load 194, and is not connected electrically to city's electrical network (not shown).Be not the voltage source of the frequency of setting local load 194 and voltage owing to have city's electrical network, transducer 166 to work incessantly.Inverter 170 is operated in electrical network parallel connection (grid-parallel) pattern, the output of adopting the mode identical with city's electrical network (not shown) to come treatment conversion device 166.

In Figure 11 B and Figure 11 E, both satisfy the bearing power demand by PV array 176 and energy storing device 164.Because there is not the when available control of solar energy, the output energy of PV array 176 can change in one day from start to finish, and, because

local load

178 or 194 also can change, transducer 166 is constantly discerned the energy requirement of

local load

178 or 194 and is regulated its power output so that to

local load

178 or 194 power supplies.The needs (for example, this can occur in weekend or vacation) that can surpass in some cases,

local load

178 or 194 from the energy of PV array 176.In these cases, 166 pairs of energy storing devices 164 of transducer charge and store any excess energy from PV array 176/ inverter 170.

Referring to Figure 12, although not shown, program 172 advantageously comprises the maximum power point tracking (MPPT) of PV array 176, inverter 170 and transformer 192, as top in conjunction with Fig. 4,6,8 discuss.Transducer 166 is dealt with the demand (that is charge or discharge) of (address) energy storing device 164.Inverter 170 is the maximum power point of Tracing PV array 176 always.Yet in addition, when being free of attachment to city's electrical network 180, thereby transducer 166 its output voltages of adjustment charge to energy storing device 164.

196 places in program 172 judge whether the PV electric power of PV array 176 is available.If, do not enter park mode at 198 places so.Park mode 198 periodically wakes up to reexamine the test at 196 places.On the other hand, if test is passed through at 196 places, so at 200 places, inverter 170 is opened.Next, at 202 places, judge whether the electric power of local load 178 or 194 is met.If,, do not judge whether suitably low from the cost (cost) of city's electrical network 180 electric power so at 204 places.If not, cut off local load 178 (or its suitable part) at 206 places, after this, repeating step 202.Otherwise,,, judge whether unnecessary available PV power so at 208 places if be met at the electric power of 202 places load 178 or 194.If not, so at 210 places, whether judgement is suitably low from the cost of the electric power of city's electrical network 180.If, then do not cut off local load 178 or 194 (or its suitable part) at 206 places.On the other hand, if suitably low from the cost of the electric power of city's electrical network 180 at 204 or 210 places, so at 212 places, transducer 166 moves as charger.Next, at 214 places, judge whether to using from the energy content of battery of for example abundance of energy storing device 164.If then repeating step 212 not.Otherwise at 216 places, transducer 166 is opened as inverter, after this, and execution in step 202.On the other hand, if having unnecessary PV power to use,, before carrying out, step 216 reduces the output of transducer 166 so at 218 places at 208 places.

Although described the specific embodiment of disclosed design in detail,, those skilled in the art will recognize that under whole instruction of the present disclosure, can develop to the multiple modification of these details with substitute.Correspondingly, disclosed specific arrangements only is exemplary, and the scope to disclosed design does not limit, and the scope of disclosed design is provided by whole ranges of claims and any and all contents of equal value.

List of numerals

2 PV array/inverter systems

4 PV arrays

6 PV arrays

More than 8 string

10 PV modules

12 inverters

14 PV array dc voltages (voltage)

16 PV array DC electric currents (amperage)

18 PV array DC power outputs (wattage)

20 100% solar radiations (i.e. " sunshine ")

22 curve charts

24 city's electrical networks

26 transformers

28 efficiency curves

30 efficiency curves

40 energy conversion efficiencies

42 energy conversion efficiencies

44 energy conversion efficiencies

46 energy conversion efficiencies

48 energy conversion efficiencies

50 multi-inverter electric power coversion systems

52 inverters

54 inverters

56 PV arrays

58 PV arrays

60 processors are as system controller

62 wattmeters

64 city's electrical networks

66 contactor K2

67 contactor K1

68 filters

69 filters

70 transformers

71 contactor K1-2

72 curve charts

74 curve charts

76 electric power coversion systems

78 circuit control devices

80 circuit control devices

82 DC buses

84 DC buses

86 curve charts

88 curve charts

90 curve charts

92 curve charts

100 programs

102 steps

104 steps

106 steps

108 steps

110 steps

112 steps

114 steps

116 steps

118 steps

120 steps

122 steps

124 steps

126 steps

128 steps

130 steps

132 steps

140 curves

142 curves

144 A

146 B

148 contravarianter voltage set-points

150 curve charts

152 curve charts

154 curve charts

160 electric power coversion systems

162 electric power coversion systems

164 energy storing devices are as the exemplary memory battery

165 first I/O

166 first transducers

167 second I/O

169 inputs

170 second inverters

171 outputs

172 programs

174 system controllers

176 PV arrays

178 local loads

180 city's electrical networks

182 controllers

184 controllers

186 wattmeters

188 filters

190 filters

191 former sides

192 transformers

193 pair sides

194 local loads

196 steps

198 steps

200 steps

202 steps

204 steps

206 steps

208 steps

210 steps

212 steps

214 steps

216 steps

218 steps

Claims

1. one kind is used for photovoltaic system (50; 76; 160; 162) power method for tracing, this system comprises several photovoltaic arrays (56,58; 176), several inverters (52,54; 170) and transformer (70; 192), this method comprises:

Operation (122,128) comprises the photovoltaic system of described several photovoltaic arrays, described several inverters and described transformer, so that provide maximum power conversion efficiency by it; And

Make and export maximization (116,122) from the power of described several photovoltaic arrays.

2. method according to claim 1 further comprises:

A plurality of photovoltaic arrays (56,58) are used as described several photovoltaic arrays; And

Output (82,84) (66) in parallel with described a plurality of photovoltaic arrays.

3. method according to claim 2 further comprises:

At noon in several hours after Zhi Qian several hour and high noon, with the output-parallel of described a plurality of photovoltaic arrays.

4. method according to claim 1 further comprises:

A plurality of photovoltaic arrays (56,58) are used as described several photovoltaic arrays;

A plurality of inverters (52,54) are used as described several inverters;

For in described a plurality of photovoltaic arrays each, by a power supply of the correspondence in described a plurality of inverters of the correspondence in described a plurality of photovoltaic arrays (122); And

Produce or be approximately during peak energy produces at peak energy, each in the independent maximum power point place of correspondence operation (122) described a plurality of photovoltaic arrays.

5. method according to claim 1 further comprises:

Determine energy and power that (60,62) city's electrical networks (64) are located;

Determine the loading on (60,62) described several inverters and the transformer; And

With the described system of optimum pressure level run (132).

6. method according to claim 1 further comprises:

A plurality of inverters (52,54) are used as described several inverters; And

For in described a plurality of photovoltaic arrays each, by corresponding in a described a plurality of photovoltaic arrays power supply (122) corresponding in described a plurality of inverters.

7. method according to claim 6 further comprises:

By in described a plurality of inverters each to transformer-supplied; And

From transformer to load (64; 178; 194) power supply.

8. method according to claim 1 further comprises:

Two photovoltaic arrays (56,58) are used as described several photovoltaic arrays;

Two inverters (52,54) are used as described several inverters;

At the beginning, with the output (82,84) (66) in parallel of two photovoltaic arrays, and by parallel connection output one (52) power supply in two inverters;

Judge when described one the power output in (120) two inverters surpasses predetermined electric power percentage, power (122) and power by one (56) in two photovoltaic arrays described (52) in two inverters with responding by another (58) in two photovoltaic arrays another (54) in two inverters;

Described one maximum power point place in two photovoltaic arrays moves described in (122) two inverters; And

In described another (122) two inverters of maximum power point place operation in two photovoltaic arrays described another.

9. method according to claim 8 further comprises:

Judge (124) when the two power output drops to and be lower than predetermined electric power percentage from two inverters; And

Preset time at interval in (132) two inverters of judgement described one when moved and be longer than the scheduled time, stop using in two inverters described one with responding, the output of two photovoltaic arrays in parallel and by parallel connection output another power supply in two inverters.

10. the method for claim 1, wherein photovoltaic system (160; 162) further comprise energy storing device (164), as the photovoltaic array (176) of described several photovoltaic arrays, as the inverter (170) and the transducer (166) of described several inverters, described method further comprises:

Transducer (166) is comprised be constructed to from energy storing device input electric power or to first I/O (165) of energy storing device output power and second I/O (167) that is constructed to import electric power or output power;

Inverter (170) is comprised be constructed to from the input (169) of photovoltaic array input electric power and the output (171) that is constructed to output power; And

The output that transformer (192) is comprised be connected electrically to inverter and to the former side (191) of second I/O of transducer and be connected electrically to local load (178) and city's electrical network (180) at least one pair side (193).

11. photovoltaic system (160; 162), comprising:

Energy storing device (164);

Photovoltaic array (176);

Transducer (166), it comprises and being constructed to from energy storing device input electric power or to first I/O (165) of energy storing device output power and second I/O (167) that is constructed to import electric power or output power;

Inverter (170), it comprises and is constructed to from the input (169) of photovoltaic array input electric power and is constructed to the output (171) of output power; And

Transformer (192), it has the output that is connected electrically to inverter and to the former side (191) of second I/O of transducer and be connected electrically to local load (178; The pair side (193) of at least one 194) and in city's electrical network (180).

12. photovoltaic system (160 as claimed in claim 11; 162), wherein, energy storing device is selected from battery, electric double layer capacitor, farad capacitor device, electrochemical double layer capacitor (EDLC) and ultracapacitor.

13. photovoltaic system (160 as claimed in claim 11; 162), wherein, inverter is constructed to provide by the output voltage of adjusting photovoltaic array the maximum power tracing of photovoltaic array, so as from the reception maximum power.

14. photovoltaic system (160 as claimed in claim 11; 162), wherein, first I/O of transducer is imported electric power from energy storing device; Wherein, second I/O of transducer is exported electric power; And wherein, local load is passed through transformer-supplied by transducer and inverter.

15. photovoltaic system (160 as claimed in claim 14; 162), wherein, transducer is constructed to as the voltage source operation and uses frequency and the voltage that local load is set from the available power of energy storing device.

16. photovoltaic system (160 as claimed in claim 11; 162), wherein, first I/O of transducer is to the energy storing device output power; Wherein, second I/O of transducer is imported electric power; And wherein, local load is passed through transformer-supplied by inverter.

17. photovoltaic system (160 as claimed in claim 16; 162), wherein, transducer is to be constructed to active rectifier that energy storing device is charged.

18. photovoltaic system (160 as claimed in claim 17; 162), wherein, second I/O of active rectifier is crossed transformer-supplied by civil power Netcom.

19. photovoltaic system (160 as claimed in claim 11; 162), wherein, first I/O of transducer is to the energy storing device output power; And wherein, second I/O of transducer is from the output input electric power of inverter.

20. photovoltaic system as claimed in claim 19 (160), wherein, local load or city's electrical network are not powered; And wherein, second I/O of transducer is directly imported electric power by the output of inverter.

21. photovoltaic system as claimed in claim 11 (162), wherein, the pair side of transformer only is connected electrically to local load (194); Wherein, first I/O of transducer is imported electric power from energy storing device; Wherein, second I/O of transducer is exported electric power; And wherein, local load is passed through transformer-supplied by transducer and inverter.

22. photovoltaic system as claimed in claim 21 (162), wherein, transducer is constructed to move and be provided with as voltage source the frequency and the voltage of local load (194); And wherein, inverter is constructed to follow the trail of the frequency and the voltage of local load.

23. electric power coversion system (50; 76; 160; 162), comprising:

Several photovoltaic arrays (56,58; 176);

Several inverters (52,54; 170);

Transformer (70; 192); And

Processor (60), it is configured (100) and is described several inverters of control and operation (122,128) described electric power coversion system, so that maximum power conversion efficiency to be provided by described several photovoltaic arrays, described several inverters and described transformer, and make power output maximization (116,122) from described several photovoltaic arrays.

24. electric power coversion system as claimed in claim 23 (76), wherein, described several photovoltaic arrays are two photovoltaic arrays (56,58) that have output (82,84) separately; Wherein, described several inverters are two inverters (52,54); And wherein, described processor (60) is configured (100) for selectively making: (a) one of correspondence power supply (66,122) by correspondence in two photovoltaic arrays in the inverter; Or (b) output-parallel of two photovoltaic arrays is electrically connected (66,132), and in two inverters one is by parallel connection output power supply.